3h-1,2,3-benzodithiazole-2-oxides

ABSTRACT

A GROUP OF 3H-1,2,3-BENZODITHIAZOLE - 2 - OXIDES WHICH MAY HAVE VARIOUS SUBSTITUENTS IN THE 4-, 5-, 6- AND 7POSITIONS ARE PREPARED BY HYDROLYSIS OF THE CORRESPONDING 1,3,2-BENZOTHIAZATHIOLIUM CHLORIDES. THE COMPOUNDS POSSESS UTILITY AS POST-EMERGENT HERBICIDES AND DYESTUFF INTERMEDIATES.

Patented Apr. 30, 1974 US. Cl. 260-304 3 Claims ABSTRACT OF THE DISCLOSURE A group of 3H-1,2,3-benzodithiazole 2 oxides which may have various substituents in the 4-, 6- and 7- positions are prepared by hydrolysis of the corresponding 1,3,2-benzothiazathiolium chlorides. The compounds possess utility as post-emergent herbicides and dyestuff intermediates.

This is a division of US. patent application Ser. No. 80,204, filed Oct. 12, 1970, which is a continuation of US. Ser. No. 777,158, filed Nov. 19, 1968, now abandoned.

DESCRIPTION OF INVENTION We have discovered a novel class of 3H-1,2,3-benzodithiazole-Z-oxides which are eifective as selective herbicides, particularly against some common broadleaf Weeds in crops such as wheat, barley, oats and corn.

The novel compounds belong to a group represented by the structural formula:

in which substituents at positions 4-, 5-, 6- and 7- are selected from the following groups:

at position 4-: H, Cl-, CH CF F and CH O- at position 5-: H, Cl-, CH and CF;,-

at position 6-: H, Cl-, CH O and CH S at position 7-: H, Cland CH,

The compounds are prepared by hydrolysis of the corresponding 1,3,2-benzothiazathiolium chlorides, as discussed as follows.

PREPARATION OF 1,3,Z-BENZOTHIAZATHIOLIUM CHLORIDES (I) Three general methods may be used to prepare the intermediate benzothiazathiolium chlorides: Method A is the original procedure of Herz, as recently described in more detail by Huestis, Walsh and Hahn (2). One mole of the aniline in glacial acetic acid is treated with seven moles of sulfur monochloride. Method B is a modification of method A in that the aniline is first converted to the hydrochloride and the molar excess of sulfur monochloride is only 3.5 fold. Under these conditions, the elemental sulfur byproduct is no longer soluble in the reaction mixture, but can easily be removed following the hydrolysis step. Method C, the novel procedure of Huestis, Walsh and Hahn (2), uses the reaction of ortho-aminobenzenethiol hydrochlorides with thionyl chloride. Since the reaction of sulfur monochloride with anilines unsubstituted in the para position invariably results in chlorination at that position, method C is recommended for those 3H-1,2,3-benzodithiazole-2-oxides having hydrogen at the 6-position.

The choice between the use of an aniline or its hydrochloride is not entirely arbitrary. With 2,5-dimethylaniline and o-trifiuoromethyl aniline, method A produces only tars and non-hydrolyzable solids, while method B gives the the desired products in good yields.

PREPARATION OF 3Hl,2,3-BENZODITHIAZOLE Z-OXIDES (II) An aqueous slurry of the benzothiazathiolium chloride is stirred at room temperature for about one hour. The solid is collected, dissolved in methanol and treated with activated charcoal. Addition of water to the filtered solution gives the product as a colorless, or pale violet, crystalline solid. Further purification by recrystallization is impractical, as even brief heating in any of a variety of solvents causes extensive decomposition of sulfur dioxide.

REFERENCES TO SYNTHESIS PROCEDURES (1) Herz, R. (to Cassella & Co.), German Pat. 360,690 (Oct. 6, 1922).

(2) Huestis, L., Walsh, M., Hahn, N., J. Org. Chem., 30, 2763 (1965) and references therein.

(3) Warburton, W. K., Chem. Rev., 57, 1011 (1957).

SPECIFIC COMPOUNDS Specific 3H-1,2,3-benzodithiazole 2-oxides which have been prepared and the methods of preparation, melting points and analytical data are shown in Table I.

TABLE I 3H-1,2,3-benzodithiazole 2-oxides Analysis (percent) Carbon Hydrogen Nitrogen Substituents M.P. Oalcu- Calcu- Calcu- 4 5 6 7 C.) lated Found lated Found lated Found Cl H O1 1 01 A 132-5 26. 24 27. 67 0. 73 0. 5. 10 5. 27 H C1 C1 1 01 A 131-3 26.24 26.82 0. 73 0. 88 5. 10 5. 45 OH: H 01 1 H A 126-7 38. 27 38. 77 2. 74 3. 02 6. 38 6. 53 CH: CH: Cl 1 H A 139- 10 41. 11 41. 3. 45 3. 59 5. 99 5. 76 OH; H 01 1 CH3 B 123-5 41. 11 41. 76 3. 45 3. 23 5. 99 6. 15 OF; H 01 1 H B 1334 30. 72 30. 12 1. 11 1. 50 5. 12 5. 28 H OF; H H C 124-7 35. 14 36. 11 1. 69 2. 03 5. 86 6. 21 OOH: H OOH; 01 B 140-3 36. 16 35. 61 3.03 3. 04 5. 27 5. 48 H H SCH; H B 121 38. 68 39. 23 3. 25 3. 59 6. 45 6. 86 F H 01 1 H A 107-8 32. 22 31. 82 1. 35 1. 74 6. 26 6. 81 H 01 H H 0 129-31 35. 03 38. 40 1. 96 2. 28 6. 81 7. 53 C1 C1 C1 H A 119 26. 24 23. 47 0. 73 1. 54 5. 10 4. 83 CH: Cl 01 H A 121-3 32. 34. 68 2. 37 2. 01 5. 49 6. 14 OOH: H OCH; H B 13540 41. 54 37. 93 3. 92 3. 28 6. 06 5. 61

1 This chlorine was introduced during the synthesis. 1 This chlorine was present in the starting aniline.

with evolutionv 3 USE OF THE COMPOUNDS AS HERBICIDES Post-emergence herbicidal activity and selectivity of the compounds listed in Table I were evaluated according to the following procedure:

4 is preferably applied as a dispersion in a diluent such as water, obtained with the aid of a surface active agent. For shipping and storage prior to dilution and application the herbicides are formulated in the customary manner with a surface active agent and a relatively small amount (1) Post emergence ac ivi y 5 of a solvent, oil or inert solid as a diluent. Both emulsifi- An aqueous dispersion of each active compound was able concentrates and wettable powders are useful and efprepared by combining 0.4 gram of the compound with fectlve fm'mulatlons' about 4 ml. of a solvent-emulsifier mixture (3 parts of a commercial polyoxyethylated vegetable oil emulsifier, one EXAMPLE 2 part xylene, one part kerosene) and then adding water, 4,6,7-trichloro 3H 1,2,3 benzodithiazole 2-oxide was with stirring, to a final volume of 40 ml. employed in combination with a surface active agent and The species of plants on which each compound was to a diluent as in Example 1. The test species of plants inbe tested were planted in four-inch pots in a greenhouse. eluded lambs-quarters, pigweed, kochia, green foxtail, Ten to eighteen days after emergence of the plants, three sugar beets and wheat. Complete control was obtained on pots were sprayed with an aqueous dispersion of the ac- P g at application rates as low as 1/2 P acre- At tive compound prepared as described above, at a rate of 5 1 l p acre i j y to Sugar beets and Wheat Was y 1b. of active compound per acre and at a spray volume of sllght. t 1/2 P acre there 110 discernible effect 60 gallons per acre. Approximately one Week after the 0H elthef Sugar beets W F spray application the plants were observed and the re- The 3H-1,2,3-be11ZPd1th1a01e'2-0X1de$ are y c011- sults rated according to the following Schedule; verted to corresponding amlnomercaptans under alkaline m M E conditions and may be used to manufacture thioindigoid mg) i 9 vat dyestuffs and substituted phenothiazines. The novel I Z 1g 6 compounds disclosed herein may be used to make subgrw 1 1 crate e ect stituted phenothiazines which have not been previously F=format1ve effect (abnor- 3=severe effect available mal form of growth) 4=manlmun etifegt d Wha.E is claimed is:

a P an 8 1e 1. 6 chloro 4 trifluoromethyl-3H-1,2,3-benzodithi- Results are tabulated below in Table II. azole-Z-oxide.

TABLE II Post emergence use of 3H-l,2,3-benzodithiazole-2oxldes So Cot- R d- Substituents Millet bea fn ton Alfalfa Oats Corn Flax i sh l a ei t Wheat sorgi x Tomato 4,6,7-trichloro- 4 2 4 3 1 1 2 2 4 2 1 2 5,6,7-trich1or0- 2 1 3 3 0 1 2 2 4 1 1 4 6-chloro-4-methyl- 3 2 4 4 1 1 2 3 4 2 1 2 6-eh1oro-4,5-dimethyl- 1 1 3 2 1 1 1 1 3 1 1 3 6-chloro-4,7-dimethyl- 4 4 3 2 2 1 3 3 4 2 3 3 6-ch1oro-4-trifluoromethyl- 3 4 4 1 1 4 4 4 1 1 4 5-tn'fluromethyl- 4 2 4 2 1 2 2 4 4 3 2 4 7-chlor0-4,6-dimethoxy- 2 1 2 1 1 1 2 1 4 1 1 4 6-methy1mercapto-.- 3 1 1 2 4 1 1 1 0 1 1 1 6-chloro-4-fluoro- 2 3 4 3 1 1 2 2 4 1 1 4 5-chloro 2 2 3 2 1 1 1 1 3 1 0 2 4,5,6-tricl1loro 2 3 4 4 1 '1 4 2 4 1 1 4 5,6-dichloro-4-methy a 4 3 4 1 1 2 2 4 1 2 3 4,6-dimethoxy- 1 1 1 1 0 0 1 1 1 1 0 1 Use of the novel compounds to combat undesired plant growth is further illustrated by the following examples.

EXAMPLE 1 6-chloro 4,7 dimethyl 3H 1,2,3 benzodithiazole 2-oxide was employed as a post-emergence herbicide at 2 1b., 1 lb. and /2 lb. per acre according to the procedure outlined above against the following plants: green foxtail, wild mustard, pigweed, wild buckwheat, lambs-quarters, corn cockle, morning glory, wheat, barley, oats and corn. At all three application rates complete control was obtained on wild mustard and pigweed with only slight cffect on barley and oats. Below 2 lb. per acre the effect on wheat and corn was also only slight. At 2 lb. per acre complete control was also obtained on lambs-quarters and morning glory.

In order to obtain uniform application of a small amount of active substance over a large area, the herbicide 2. 5 trifluoromethyl 3H 1,2,3 benzodithiazole-2- oxide.

3. 4,6 dimethoxy 3H 1,2,3 benzodithiazole 2- oxide.

References Cited US. Cl. XJR. 

